SQL Server 2019

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CREATE TABLE t(date_from date, date_to date, person varchar(7), tax int);
INSERT INTO t(date_from, date_to, person, tax) VALUES
('2020-01-30', '2020-02-02', 'person1', 20),
('2020-01-30', '2020-01-31', 'person1', 10),
('2020-02-01', '2020-02-03', 'person1', 15);
3 rows affected

WITH cte AS (
    SELECT person, ca.*
    FROM t
    CROSS APPLY (VALUES
        (date_from, tax),
        (date_to, 0),
        (DATEADD(DAY, 1, date_to), -tax)
    ) AS ca(date, value)
)
SELECT person, date, SUM(SUM(value)) OVER (
    PARTITION BY person
    ORDER BY date
) AS tax_value
FROM cte
GROUP BY person, date
ORDER BY person, date


person
date
tax_value


person1
2020-01-30
30

person1
2020-01-31
30

person1
2020-02-01
35

person1
2020-02-02
35

person1
2020-02-03
15

person1
2020-02-04
0

person	date	tax_value
person1	2020-01-30	30
person1	2020-01-31	30
person1	2020-02-01	35
person1	2020-02-02	35
person1	2020-02-03	15
person1	2020-02-04	0